In recent years, progress has been made in the research and development of application of a coating method such as an inkjet method to an organic electronic device manufacturing method and an organic EL device manufacturing method. Formation of organic functional films by using a coating method is flexible to increase in size of devices in the future, compared to the case of using a vacuum film-forming method such as a vapor deposition method, and is therefore advantageous for volume production.
In the case of manufacturing an organic electronic device or an organic EL device using film formation by a coating method, a bank is formed so as to surround an area on which the film is to be formed, and organic functional material ink is applied within the aperture defined by the bank. In this case, a problem (hereinafter, “climbing phenomenon”) would occur, in which the upper edge of the organic functional material ink applied within the aperture remains at a higher position than a predetermined position on the surface of the sidewall of the bank facing the aperture. In other words, the upper edge of the organic functional material ink would be located closer to the upper edge of the opening.
If such a climbing phenomenon occurs, it would be impossible to ensure the desired device performance. Specifically, if the climbing phenomenon occurs during the process of manufacturing an electronic device having a plurality of organic functional films within an aperture, and electrodes are provided to sandwich the organic functional films, the order of the organic functional films would deviate from the design specification, and a leak current path could be formed. Therefore, if such a phenomenon occurs, it would be impossible to ensure the desired device performance.
Patent Literatures 1 and 2 disclose technology of preventing the occurrence of such a climbing phenomenon. According to the technology disclosed in Patent Literature 1, a first bank surrounding an aperture is formed, and after applying organic functional ink within the aperture, a second bank is formed so as to cover the surface of the sidewall of the bank facing the aperture and a portion of the organic functional layer formed on the surface of the sidewall, and then another drip of the organic functional ink is applied within the aperture surrounded by the second bank.
According to the technology disclosed in Patent Literature 2, a second bank having a smaller cross-section than a first bank is layered on the first bank such that the portion (stair-shape portion) of the upper surface of the first bank that is not covered with the second bank has a higher degree of liquid-repellency than the surfaces of the first bank other than the stair-shape portion and the surfaces of the second bank, aiming to prevent the occurrence of the climbing phenomenon.